This invention is directed to an apparatus and method for the electronic damping of resonances by sensing resonance vibration in a structure and feeding an appropriately processed damping force back into the structure for damping thereof.
Mechanical structures are used for a number of different purposes including the support of instrumentation equipment, optical elements and the like.
Gimbals fall in this class and are used for supporting optical and other elements in such a way that they may be rotated on one or more axes. When the mechanical gimbal structure has a mechanical resonance it reduces the effectiveness of the equipment mounted thereon. To overcome such resonances, mechanical stiffening of the structure has been common. In other cases, dampening weights attached by critically resilient supports have been employed to absorb and damp the resonance vibration energy of the structure. Vibration is a common problem in gimbal systems that have the torquer drive motor separated from the rate and position sensors by the mechanical structure of the gimbal. If the gimbal is flexible and has one or more resonance modes, then resonant peaks will be seen in the torquer response. If the frequency of the resonance is sufficiently low and the mechanical Q of the structure is high enough, this resonance can be a source of torquer control loop oscillations and sometimes causes loss of loop control. Even if the resonance problem is not sufficiently severe to produce oscillation, it can still have a significant effect on the torquer response. As a result, the speed of response of a torquer control loop is usually limited by the lowest resonant frequency of the gimbal. When mechanical stiffening of the gimbal ring is employed, there are weight and cost penalties as well as penalties in the response time for rotation of the axis. Such gimbals are often supplied with a torquer motor and a position sensor which feeds back position information to the torquer motor driver. Damping of high frequency resonances can be accomplished by inserting a filter in the electronic portion of the torquer loop but this lowers the servo response time.
Efforts have been made to apply piezoelectric transducers to mechanical structures for the damping of resonance vibration therein, but such piezoelectric devices are limited in power and cannot supply enough damping power to be useful. Thus there is need for an adequate solution to this vibration problem.